Metal oxide protective layer for a semiconductor device

ABSTRACT

Embodiments related to metal oxide protective layers formed on a surface of a halogen-sensitive metal-including layer present on a substrate processed in a semiconductor processing reactor are provided. In one example, a method for forming a metal oxide protective layer is provided. The example method includes forming a metal-including active species on the halogen-sensitive metal-including layer, the metal-including active species being derived from a non-halogenated metal oxide precursor. The example method also includes reacting an oxygen-containing reactant with the metal-including active species to form the metal oxide protective layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 13/439,528 entitled METAL OXIDE PROTECTIVE LAYERFOR A SEMICONDUCTOR DEVICE, filed on Apr. 4, 2012, the disclosure ofwhich is incorporated herein by reference.

BACKGROUND

Some semiconductor devices employ a high-K dielectric material (relativeto SiO₂) as a gate dielectric to achieve a desired equivalent oxidethickness (EOT) with a film that is sufficiently thick to avoidundesirable leakage. However, some high-K dielectric materials may beincompatible with subsequently deposited materials. In some settings,the effect of such incompatibilities may compromise device performance.

SUMMARY

Various embodiments are disclosed herein that relate to forming a metaloxide protective layer on a surface of a halogen-sensitivemetal-including layer present on a substrate processed in asemiconductor processing reactor. For example, one embodiment provides amethod for forming a metal oxide protective layer comprising forming ametal-including active species on the halogen-sensitive metal-includinglayer, the metal-including active species being derived from anon-halogenated metal oxide precursor. The example method also includesreacting an oxygen-containing reactant with the metal-including activespecies to form the metal oxide protective layer.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Furthermore,the claimed subject matter is not limited to implementations that solveany or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows film stack thickness and uniformity data for discontinuousHfO₂ films on a SrTiO₃ film using a halogen-including film precursor andschematically shows example surface topography for some of thosediscontinuous HfO₂ films.

FIG. 2 shows film stack thickness and uniformity data for discontinuousHfO₂ films on halogen-sensitive high-K films comprising varying amountsof Sr.

FIG. 3 shows a method of forming a metal oxide protective layeraccording to an embodiment of the present disclosure.

FIG. 4 shows film stack thickness and uniformity data for HfO₂ filmsformed on a metal oxide protective layer having an underlying SrTiO₃film according to an embodiment of the present disclosure.

FIG. 5 shows a method of forming a gate assembly for a semiconductordevice according to an embodiment of the present disclosure.

FIG. 6 schematically shows a film stack for a semiconductor deviceaccording to an embodiment of the present disclosure.

FIG. 7 schematically shows another film stack for a semiconductor deviceaccording to an embodiment of the present disclosure.

FIG. 8 shows a semiconductor process tool according to an embodiment ofthe present disclosure.

DETAILED DESCRIPTION

Modern semiconductor devices may include high-K gate dielectricmaterials to improve device performance relative to devices employingSiO₂ gate dielectric at a given architectural size. The thickness of thegate dielectric material may shrink with the transistor size to providea desired gate capacitance and/or drive current. The physical thicknessof a SiO₂ gate dielectric may eventually become small enough so thatleakage from the gate to the channel (e.g., from tunneling effects)raises power dissipation in the device to unacceptably high levels.

One approach to mitigate this effect is to replace the SiO₂ gatedielectric with a gate dielectric material having a dielectric constantvalue (K) that is relatively higher than the dielectric constant forSiO₂ (K˜3-4). For example, some semiconductor devices employ HfO₂(K˜20-25), which may provide an equivalent oxide thickness (EOT) to aphysically thinner layer of SiO₂. In turn, a gate including a high-Kgate dielectric material may provide similar device turn-oncharacteristics while mitigating gate leakage and power dissipation.

As used herein, a high-K dielectric material refers to any suitabledielectric material having a dielectric constant greater than SiO₂.Accordingly, some transition metal oxides such as HfO₂ and TiO₂ (K˜50)may be considered high-K dielectric materials. Some non-transitionmetal-including oxides such as Al₂O₃ (K˜8) may be considered high-Kdielectric materials. Some high-K dielectric materials may have adielectric constant of 200 or more (e.g., ultra-high-K dielectricmaterials), such as some alkaline earth metal-including metal oxides.For example, SrTi_(x)O_(y), BaTi_(x)O_(y), SrO, andSr_(x)Ba_((1-x))Ti_(y)O_(z) may be considered high-K dielectricmaterials.

Once the gate dielectric layer is formed, other dielectric or conductivelayers may be formed on top of the gate dielectric layer to build thegate assembly. Because many high-K dielectric materials include one ormore kinds of metal cations in an oxide lattice, the surface of thehigh-K dielectric material may include vacancies, defects, or chargelocations that may facilitate chemical reactions during formation of alayer on top of the high-K dielectric material. Such reactions may besensitive to the process chemistry used when forming the subsequentlayer and to the reaction conditions under which the subsequent layer isformed. In some cases, these reactions may be undesirable. For example,such reactions may lead to the generation of undesirable layermorphology, the formation of non-uniform films, or the nucleation ofinterfacial or other defects. In turn, device performance may bedegraded or destroyed.

As an example, some high-K dielectric materials may be sensitive tohalogens. As used herein, a halogen-sensitive surface or layer refers toa surface or layer that is reactive with a halogen-including chemical(e.g., a reactant or film precursor), or that facilitates reaction of ahalogen-including chemical (e.g., a decomposition reaction or othersurface reaction), under the conditions at which the halogen-sensitivesurface is exposed to the halogen-including chemical. In some settings,a halogen-sensitive surface may be reactive with a halogen-includingchemical in an undesirable manner or facilitate an undesirable reactionof a halogen-including chemical. In some settings, a halogen-sensitivesurface may be reactive with or facilitate a reaction of ahalogen-including chemical in a manner that leads to an undesirablemorphology, thickness, density, uniformity, or other characteristic in afilm that is formed on top of the halogen-sensitive surface.

Accordingly, the embodiments described herein are related to forming ametal oxide protective layer on a surface of a halogen-sensitivemetal-including layer present on a substrate processed in asemiconductor processing reactor. As used herein, a metal oxideprotective layer comprises a metal oxide layer that is less sensitive toa halogen-including chemical than the halogen-sensitive metal-includinglayer under the conditions at which the metal oxide protective layer isexposed to the halogen-including chemical. In some embodiments, themetal oxide protective layer may act as a barrier or a buffer layer tophysically cap an underlying halogen-sensitive metal-including layer.For example, in some embodiments, a metal oxide protective layer may bedeposited on top of the halogen-sensitive metal-including layer. In someembodiments, a metal oxide protective layer may be formed from at leasta portion of a surface of the halogen-sensitive metal-including layer.

For example, one embodiment provides a method for forming a metal oxideprotective layer comprising forming a metal-including active species onthe halogen-sensitive metal-including layer, the metal-including activespecies being derived from a non-halogenated metal oxide precursor. Theexample method also includes reacting an oxygen-containing reactant withthe metal-including active species to form the metal oxide protectivelayer. Once formed, the metal oxide protective layer may shield theunderlying halogen-sensitive metal-including layer from subsequentexposure to halogen-including chemicals.

The embodiments described herein are also related to methods offabricating a semiconductor device. For example, one embodiment providesa method comprising forming a halogen-sensitive gate dielectric materialon a substrate. The example method also comprises forming a metal oxideprotective layer on an exposed surface of the halogen-sensitive gatedielectric material by reacting a metal-including active species derivedfrom a non-halogenated metal oxide precursor with an oxygen-containingreactant. Finally, the example method comprises forming ametal-including film on top of the metal oxide protective layer byexposing the metal oxide protective layer to a halogen-including metalcompound.

Some high-K films that include alkaline earth metals may includehalogen-sensitive metal-including materials. For example, FIG. 1 showsfilm stack thickness and uniformity data 100 collected via ellipsometryfor HfO₂ films deposited using a halogen-including film precursor on ahalogen-sensitive SrTiO₃ high-K film. Film stack thickness anduniformity data 100 includes film stack non-uniformity data 102, whichdescribes the within-substrate non-uniformity of the SrTiO₃/HfO₂ stack.Within-substrate non-uniformity may be calculated by measuring asuitable number of locations on the substrate surface (e.g., 49measurement sites, though any suitable number of locations may bemeasured) and dividing the standard deviation of the measured thicknessdata by the average thickness. The calculated non-uniformity value maybe expressed as a percentage by multiplying the result by 100. Filmstack thickness and uniformity data 100 also includes film stack meanthickness data 104, which describes the total stack thickness.

The HfO₂ films shown in FIG. 1 were deposited using HfCl₄ via an atomiclayer deposition (ALD) technique. Film stack non-uniformity data 102 andfilm stack mean thickness data 104 are functions of varying numbers ofdoses or pulses of HfCl₄ to the substrate surface. Employing controlledsurface reactions, ALD typically provides layer-by-layer film depositionon an underlying surface. Film thickness may be built up by repeated,separated exposures of the surface to film precursors and reactants.Consequently, ALD deposition processes may provide highly-controllablefilm thickness and uniformity on surfaces with three-dimensional surfacetopography, such as stepped surfaces and the like. An ALD-deposited filmmay be built up to any suitable thickness by repeating a sequentialdeposition cycle where a population of surface active species formed onthe surface from one precursor subsequently reacts with a later-suppliedreactant. Under typical deposition conditions, the surface achieves somedegree of saturation of chemisorbed surface active species during thedeposition cycle, providing a potentially self-limiting depositionmechanism.

As shown in FIG. 1, film stack non-uniformity data 102 is dependent onthe amount of halogen-containing precursor supplied to the substrate,increasing to a maximum at data point 102A and falling to successivelylower values at data points 102B and 102C, respectively. Further,observed film stack mean thickness data 104 exhibits deposition ratecharacteristics that depart from expected film stack mean thickness data106. Taken together, the thickness data may suggest a surface reactionmechanism that interferes with the ordinary course of an ALD process.

Schematic depictions of top views of film surfaces corresponding to datapoints 102A, 102B, and 102C indicate that domains of HfO₂ grow fromislands. Extended deposition cycles cause the islands to merge. Thus,the large variation in thickness non-uniformity shown in film stacknon-uniformity data 102 may reflect the discontinuous nature of a filmdeposition process that proceeds by nucleating, extending, andeventually merging islands of HfO₂ film.

FIG. 2 shows ellipsometrically-measured film stack thickness anduniformity data 200 for HfO₂ films formed from HfCl₄ onhalogen-sensitive high-K films including varying amounts of Sr. Forexample, film stack non-uniformity data 202 depicts a relationshipbetween film stack non-uniformity as measured on a HfO₂ layer formed onan SrO underlayer and a number of Sr precursor pulses supplied duringSrO deposition, which corresponds somewhat to Sr content in the SrOunderlayer. Film stack non-uniformity data 204 depicts a relationshipbetween film stack non-uniformity as measured on an HfO₂ layer formed ona Sr_(x)Ti_(y)O_(z) underlayer and a number of Sr precursor pulsessupplied during Sr_(x)Ti_(y)O_(z) deposition. For both types ofSr-containing underlayer, increasing the content of Sr present in theSr-containing underlayer increases the non-uniformity in the total filmstack.

Without wishing to be bound by theory, certain surface sites onhalogen-sensitive metal-including layers may promote or retard filmdeposition when exposed to halogen-containing chemicals, leading tolocal discontinuities in the film. In the examples shown in FIGS. 1 and2, the presence and amount of Sr present on the surface exposed to HfCl₄appears to influence the degree of non-uniformity. Depending on theprocess conditions, Sr may interact with Cl liberated from HfCl₄ uponadsorption to the Sr-containing surface. The Cl may poison the surfaceby blocking Sr or Sr-coordinated sites where additional Hf-containingactive species may form. Consequently, further adsorption and formationof Hf-containing active species may preferentially occur on existingHfO₂ islands. As the deposition process proceeds, HfO₂ islands may growto displace Cl bound to the surface. Thus, the relative effect ofhalogen-sensitive sites on deposition chemistry may diminish so that theprocess transitions to a more typical layer-by-layer depositionmechanism. While the example described here relates to surface chemistrythat may be inhibited by halogen atoms, it will be understood thathalogens may promote surface reactions in a non-uniform way in somesettings. Regardless of the mechanism by which the halogen interactswith the halogen-sensitive surface, it will be appreciated that suchinteractions may disfavor the formation and propagation of continuous,uniform films.

Forming a metal oxide protective layer on top of the halogen-sensitivemetal-including layer may reduce or prevent interaction between halogenatoms subsequently supplied to the substrate. For example, a metal oxideprotective layer deposited on top of an alkaline earth metal-includingmetal oxide may prevent the poisoning or promotion of some reactions atcoordination sites proximate to alkaline earth metal atoms by occupyingthose sites.

It will be appreciated that any suitable metal oxide may be employed asa metal oxide protective layer. In some embodiments, the metal oxideprotective layer may be selected according to materials to which themetal oxide protective layer may later be exposed during subsequent filmformation and/or patterning steps, and process conditions for suchsteps. For example, in some embodiments, the metal oxide protectivelayer may exclude materials that may promote or facilitate undesirablereactions. In one scenario, the metal oxide protective layer may excludealkaline earth metals. Further, it will be appreciated that a particularmetal oxide or composition of metal oxides selected for use in a metaloxide protective layer may vary according to the kind ofhalogen-sensitive metal-including layer on which it will be formed. Insome embodiments, a metal oxide protective layer composition may beselected based on physical parameters for the metal oxide protectivelayer and/or the underlying halogen-sensitive metal-including layer. Forexample, the metal oxide protective layer composition may be selectedbased on consideration of material properties such as lattice constantsor material morphology, the sensitivity of the metal oxide protectivelayer to etch chemicals, or the ability of the metal oxide protectivelayer to regulate the diffusion of metals. In some settings, a metaloxide protective layer composition may be selected based on electricaland/or device performance considerations, such as the effect that themetal oxide protective layer may have on the EOT of a gate stack, deviceleakage, or the threshold voltage in an underlying channel.

In some embodiments, a metal oxide protective layer including a suitabletitanium oxide may be formed on a halogen-sensitive metal-includinglayer. For example, a metal oxide protective layer including TiO₂ may beformed on a halogen-sensitive high-K dielectric layer. In some settings,a TiO₂ metal oxide protective layer may be formed on an alkaline earthmetal-including metal oxide such as SrTi_(x)O_(y), BaTi_(x)O_(y), SrO,and Sr_(x)Ba_((1-x))Ti_(y)O_(z). Because TiO₂ is a high-K dielectricmaterial, a suitably thin layer of TiO₂ may have a tolerable effect ondevice EOT if included in a gate stack.

Non-transition metal oxides may also be included in a metal protectiveoxide layer in some settings. For example, Al may be included in a metaloxide protective layer in some embodiments. In one scenario, the metaloxide protective layer may comprise Al₂O₃. While Al₂O₃ has a lowerdielectric constant than TiO₂, including Al₂O₃ in a gate stack maypermit adjustment of the device's threshold voltage.

FIG. 3 shows a flowchart for an embodiment of a method 300 of forming ametal oxide protective layer comprising titanium and oxygen on ahalogen-sensitive metal-including surface of a substrate. Embodiments ofmethod 300 may be performed by any suitable hardware and software,including the hardware and software described herein. It will beappreciated that portions of the processes described in method 300 maybe omitted, reordered, and/or supplemented without departing from thescope of the present disclosure.

At 302, method 300 includes supporting a substrate in a reactor. A metaloxide protective layer may be formed on an exposed halogen-sensitivesurface of any suitable substrate without departing from the presentdisclosure. Further, the substrate may have any suitable topography,including planar and non-planar surfaces that are exposed fordeposition.

In some embodiments, supporting the substrate in the reactor may includeadjusting one or more reactor conditions, such as temperature, pressure,and/or inert gas (e.g., Ar, N₂, or He) flow rate, to conditions suitablefor film formation prior to processing the substrate. It will beappreciated that such film formation conditions may vary according tofilm deposition process chemistry, substrate surface termination, and soon.

For example, reactor conditions may be adjusted to facilitate theformation of surface active species from suitable film precursors byactivating surface adsorption and decomposition processes. Reactorconditions may also be adjusted to facilitate film formation byactivating the reaction of such surface active species with a suitablereactant, whether present in the gas phase or on the surface. In somescenarios, reactor conditions may be adjusted to avoid gas phasedecomposition reactions for one or more of precursors and/or reactants,potentially avoiding film contamination from decomposition productsand/or poor step coverage resulting from diffusion effects. Further, insome scenarios, reactor conditions may be adjusted to avoid condensationof precursors and/or reactants on various reactor surfaces, potentiallyavoiding small particle defect generation processes.

Non-limiting reactor pressures for processes used to form a metal oxideprotective layer comprising titanium and oxygen include pressuresranging from 0.1 Torr to 10 Torr, within an acceptable tolerance.Non-limiting reactor temperatures for such processes includetemperatures ranging from 100° C. to 400° C., within an acceptabletolerance. In some scenarios, processes that form a metal oxideprotective layer at a temperature nearer the lower end of the range mayprovide a faster film formation rate. This may enhance manufacturabilityof the film and/or reduce an amount of precursor consumed during filmformation. In some other scenarios, processes that form a metal oxideprotective layer at a temperature nearer the upper end of the range mayprovide a film with comparatively higher purity. For example, some metaloxide protective layers may be formed from non-halogenated metal oxideprecursors including organometallic complexes, as described in moredetail below. Using such precursors with comparatively higher processingtemperatures may decrease carbon residue in the metal oxide protectivelayer. In turn, the metal oxide protective layer may be more resistantto some etch processes.

In the example shown in FIG. 3, method 300 enters a film formation cycleafter supporting the substrate in the reactor at 302. As used herein, afilm formation cycle refers to a film formation event that includes asingle exposure of the non-halogenated metal oxide precursor and asingle exposure of an oxygen-containing reactant. It will be appreciatedthat any suitable adjustments to the reactor conditions may be madeduring the film formation cycle, including adjustments to temperature,pressure, and/or the flow rates of various gases supplied to the reactorduring the film formation cycle.

The film formation cycle shown in FIG. 3 includes processes 304 through310. It will be appreciated that the arrangement and order of processesshown in the film formation cycle depicted in FIG. 3 are provided forillustrative purposes only, and may be varied in any suitable way insome embodiments.

At 304, method 300 includes supplying a non-halogenated metal oxideprecursor to the reactor during a precursor supply portion of the filmformation cycle. Any suitable non-halogenated metal oxide precursor maybe employed without departing from the scope of the present disclosure.Non-limiting examples of non-halogenated metal oxide precursors includetransition metal alkoxides (e.g., titanium tetraethoxide (Ti(OC₂H₅)₄),titanium tetramethoxide (Ti(OCH₃)₄), titanium tetraisopropoxide(Ti(i-OC₃H₇)₄, and titanium tetra-n-butoxide (Ti(n-OC₄H₉)₄)); transitionmetal amino complexes (e.g., tetrakis(dimethylamido)titanium(Ti(N(CH₃)₂)₄) and tetrakis(diethylamido)titanium (Ti(N(C₂H₅)₂)₄));transition metal silanes (e.g., tetrakis(trimethylsilylmethyl)titanium(Ti((CH₃)SiCH₂)₄)); and transition metal cyclopentadiene complexes(e.g., η8-cyclooctatetraene)(η5-cyclopentadienyl)titanium (C₁₃H₁₃Ti),di-1,3-cyclopentadien-1-yl[bis(N-methylmethanaminato)]titanium(C₁₄H₂₂N₂Ti), and dicyclopentadienyl titanium diazide (C₁₀H₁₀N₆Ti).

While the example non-halogenated precursors described above relate totransition metals for clarity, it will be appreciated thatnon-transition metal versions may be employed in some embodimentswithout departing from the scope of the present disclosure. Asnon-limiting examples of non-halogenated non-transition metal oxideprecursors, aluminum alkyl complexes, aluminum alkoxides, aluminumsilanes, aluminum amino complexes, and aluminum cyclopentadienecomplexes may be employed in some embodiments. Further, it will beappreciated that, in some embodiments where the halogen-sensitivemetal-including layer is sensitive to a particular halogen, thenon-halogen metal oxide precursor may exclude that halogen. For example,if the halogen-sensitive metal-including layer is sensitive to chlorine,the non-halogenated metal oxide precursor may be a non-chlorinated metaloxide precursor.

It will be appreciated that the amount of the non-halogenated metaloxide precursor supplied to the reactor during process 304 may varyaccording to, among other factors, the topography of the exposed surfaceof the substrate, the film formation conditions present in the reactor,and the adsorption rate and/or the sticking coefficient of the precursoron the surface under those conditions. In one non-limiting process fordepositing the metal oxide protective layer comprising titanium andoxygen, titanium tetramethoxide (Ti(OCH₃)₄) may be supplied to thereactor in a pulse having a duration ranging from 0.5 to 20 seconds,within an acceptable tolerance, for a 300-mm substrate. In anon-limiting process for depositing a metal oxide protective layercomprising aluminum and oxygen, trimethylaluminum (Al₂(CH₃)₆) may besupplied to the reactor in a pulse having a duration ranging from 0.03to 10 seconds, within an acceptable tolerance, for a 300-mm substrate.

Without wishing to be bound by theory, as the non-halogenated metaloxide precursor is supplied to the reactor, gas phase molecules of theprecursor may adsorb on the exposed surface of the substrate. Some ofthe gas phase molecules may become chemically adsorbed (e.g.,chemisorbed) to the surface at sites on the surface that activate suchchemisorption reactions. Such chemisorbed species may form surfaceactive species of the non-halogenated metal oxide precursor, e.g., ametal-including active species derived from the non-halogenated metaloxide precursor may be formed on the surface. Because a metal-includingactive species is bound to at least one surface site until a furtherreaction occurs, adsorption of the non-halogenated metal oxide precursormay occur in a self-limiting manner. In turn, the film formed during afilm formation cycle may be moderated at least in part by the surfacereactions of the metal-including active species with asubsequently-supplied reactant, as described in more detail below.

In some embodiments, a full monolayer of metal-including active speciesmay be formed in each film formation cycle. In some other embodiments,less than a full monolayer of metal-including active species may beformed in each deposition cycle. For example, in some embodiments forforming a metal oxide protective layer comprising titanium and oxygen ona halogen-sensitive metal-including layer that includes Sr, each filmformation cycle may deposit approximately 0.5 Å of film. In anotherexample where a metal oxide protective layer including aluminum andoxygen is formed, each film formation cycle may deposit approximately 1Å of film.

It will be appreciated that relative amounts of the non-halogenatedmetal oxide precursor may be supplied to the reactor according to anysuitable technique. Non-limiting examples include controlling mass orvolume flows of vapor or liquid precursor sources using suitable valves,flow controllers, pressure controllers, and so on. Other examplesinclude, but are not limited to, controlling precursor supply via aphase change from one state to another, such as by controllingtemperatures and/or pressures of liquid or solid precursor sources.

At 306, method 300 includes removing the non-halogenated metal oxideprecursor from the reactor. Removing the non-halogenated metal oxideprecursor from the reactor includes removing gas phase molecules of theprecursor and molecules of the precursor that are condensed on thesurface but that are not chemically adsorbed to it. Such physicallyadsorbed (e.g., physisorbed) molecules may be condensed on the surfacein more than one layer or may be distributed in non-uniform ways (suchas being condensed within narrow openings formed in the exposedsurface). Removing non-chemisorbed precursor molecules may preventreaction of such molecules with subsequently-introducedoxygen-containing reactant. In turn, it may be possible thatnon-uniform, non-conformal film formation and/or small particle defectgeneration that may result from residual, non-chemisorbed molecules ofthe precursor may be avoided.

It will be appreciated that any suitable approach for removing residualnon-halogenated metal oxide precursor from the reactor may be employedwithout departing from the scope of the present disclosure. For example,in some embodiments, the reactor may be evacuated to a base pressure.Additionally or alternatively, in some embodiments, the reactor may besupplied with a suitable displacement gas, such as Ar, N₂, or He. In onenon-limiting example of a process used to form a metal oxide protectivelayer comprising titanium and oxygen, the reactor may be purged orevacuated for at least 0.1 second, within an acceptable tolerance, toremove residual non-halogenated metal oxide precursor from the reactor.

Similar purge or evacuation times may be employed when forming a metaloxide protective layer comprising aluminum and oxygen.

At 308, method 300 includes supplying an oxygen-containing reactant tothe reactor. Without wishing to be bound by theory, theoxygen-containing reactant may be activated to form gas-phase activatedspecies and/or surface-adsorbed activated species. Such activatedspecies may react with metal-including active species on the exposedsurface of the substrate to form the metal oxide protective layer.Because the population of metal-including active species may moderatethe film deposition rate somewhat, the reaction between themetal-including active species and the activated species formed from thereactant may be comparatively fast, potentially avoiding thicknessnon-uniformity that might otherwise result from mass transport effects.

Any suitable oxygen-containing reactant may be employed withoutdeparting from the scope of the present disclosure. Non-limitingexamples of oxygen-containing reactants that may be used include O₂, O₃,and H₂O. In one non-limiting example of a process used to form a metaloxide protective layer comprising titanium and oxygen, H₂O may besupplied in a pulse having a duration ranging from 1 to 20 seconds,within an acceptable tolerance, for a 300-mm substrate. In anon-limiting process used to deposit a metal oxide protective layercomprising aluminum and oxygen, H₂O may be supplied in a pulse having aduration ranging from 0.05 to 10 seconds, within an acceptabletolerance, for a 300-mm substrate.

At 310, method 300 includes removing the oxygen-containing reactant fromthe reactor. Removing the oxygen-containing reactant from the reactorincludes removing gas phase molecules and surface-adsorbedoxygen-containing reactant. Removing residual oxygen-containing reactantmay prevent unwanted gas phase or surface reactions that may result fromintroduction of non-halogenated metal oxide precursor during asubsequent layer formation cycle. In turn, non-uniform, non-conformalfilm formation and/or small particle defect generation resulting fromreaction between residual oxygen-containing reactant molecules and theprecursors may be avoided.

It will be appreciated that any suitable approach for removing residualoxygen-containing reactant from the reactor may be employed withoutdeparting from the scope of the present disclosure. For example, in someembodiments, the reactor may be evacuated to a base pressure.Additionally or alternatively, in some embodiments, the reactor may besupplied with a suitable displacement gas, such as Ar, N₂, or He. Itwill be appreciated that, in some embodiments, processes for removingresidual oxygen-containing reactant may vary from processes for removingthe precursors. For example, it may take longer to purge the reactantfrom the reactor due to a comparatively greater sticking coefficient forthe reactant relative to the precursors. In one non-limiting example ofa process used to form a metal oxide protective layer comprisingtitanium and oxygen, the reactor may be purged or evacuated for at least1 second, within an acceptable tolerance, to remove residualoxygen-containing reactant from the reactor. In a non-limiting exampleof a process used to form a metal oxide protective layer comprisingaluminum and oxygen, the reactor may be purged or evacuated for at least0.1 second, within an acceptable tolerance.

Because the metal oxide protective layer may be formed via aself-limiting adsorption and reaction film formation process, in someembodiments, each film formation cycle may yield a predictable thicknessof film, within an acceptable tolerance. Consequently, in some of suchembodiments, any suitable thickness of metal oxide protective layer maybe formed by repeating the film formation cycle a suitable number oftimes. Thus, method 300 includes, at 312, determining whether to formanother layer of the metal oxide protective layer. If another layer isto be formed, method 300 returns to 304; if not, film formation iscompleted and the substrate is removed from the reactor at 314.

While method 300 generally describes an atomic layer deposition filmformation process, it will be appreciated that any suitable filmformation process may be employed to form the metal oxide protectivelayer without departing from the scope of the present disclosure. Insome embodiments, the layer-by-layer film formation process provided byALD may permit precise, predictable control of the thickness of themetal oxide protective layer. However, in some embodiments, chemicalvapor deposition (CVD) may be employed, as CVD techniques typically formfilms at a relatively faster deposition rate than ALD processes.Further, it will be appreciated that some embodiments of the filmformation processes described herein may cause the metal oxideprotection layer to relax into or consume portions of an upper layer ofthe halogen-sensitive metal-including film.

It will be appreciated that the metal oxide protective layer may beprovided in any suitable thickness. FIG. 4 showsellipsometrically-measured film stack thickness and uniformity data 400for HfO₂ films of a constant thickness formed via an HfCl₄ precursor onvarying thicknesses of embodiments of a TiO₂ metal oxide protectivelayer. The example TiO₂ metal oxide protective layers represented inFIG. 4 were deposited on identical halogen-sensitive SrTiO₃ films. Filmstack non-uniformity data 402 depicts a relationship between the numberof TiO₂ film formation cycles, which is proportionate to the thicknessof TiO₂ film deposited on the surface of the SrTiO₃ film, and thenon-uniformity of a film stack having an HfO₂ film on top.

As shown by film stack non-uniformity data 402, increasing the thicknessof the TiO₂ film decreases the film stack non-uniformity. For example,film stacks having at least 3 TiO₂ film formation cycles (correspondingto approximately 1.5 Å of a TiO₂ metal oxide protective layer in thisexample) exhibit approximately 13% within-substrate non-uniformity ontop of the TiO₂ layer. Film stacks that include 2.5 Å of a TiO₂ metaloxide protective layer formed from 5 film formation cycles exhibitapproximately 3% within-substrate non-uniformity on top of the TiO₂layer. A 5 Å layer of a TiO2 metal oxide protective film may exhibit awithin-substrate uniformity of approximately 2%, and a 20 Å layer of aTiO₂ metal oxide protective film may exhibit a within-substrateuniformity of approximately 1%.

Further, mean film stack thickness data 404 may indicate that dramaticchanges in surface non-uniformity may be achieved using metal oxideprotective layers that occupy just a fraction of the total film stack.For the example 5-cycle TiO₂ metal oxide protective layer shown in FIG.4, the mean film stack thickness is approximately 46 Å, only 2.5 Å ofwhich is occupied by the TiO₂ metal oxide protective layer. Thus, theTiO₂ metal oxide protective layer represents 5% or less of the totalfilm stack. Thus, even relatively thin films of metal oxide protectivelayers may provide a substantial enhancement in the uniformity of filmstacks. Moreover, in the example shown in FIG. 4, mean film stackthickness data 404 depicts an approximate 10% decrease in film stackthickness for film stacks that include a 5-cycle TiO₂ metal oxideprotective layer. This may suggest a decrease in discontinuities (e.g.,islands) in the HfO₂ film. Consequently, embodiments of metal oxideprotective layers may provide an approach to permit halogen-sensitivemetal-including layers to be used with halogen-based film formationprocesses when forming device structures where device performance isstrongly dependent on device structure dimensionality (e.g., devicestructure thickness).

For example, FIG. 5 shows an embodiment of a method 500 of forming agate assembly for semiconductor device, the gate assembly including ametal oxide protective layer. At 502, method 500 comprises forming ahalogen-sensitive gate dielectric layer on a substrate. In someembodiments, the halogen-sensitive gate dielectric layer may be formedvia a suitable ALD process, though it will be appreciated that anysuitable process for forming the gate dielectric layer may be employedwithout departing from the scope of the present disclosure.

At 504, method 500 comprises forming a metal oxide protective layer onthe halogen-sensitive gate dielectric layer. As described in more detailbelow, any suitable thickness of metal oxide protective layer may beformed according to an embodiment of method 300. In some embodiments,the metal oxide protective layer may be formed in the semiconductorprocessing tool or reactor used to form the gate dielectric layer. Thismay prevent exposure of the gate dielectric layer to a vacuum and/or airbreak that might form an undesirable adlayer on top of the gatedielectric layer, potentially altering one or more electricalcharacteristics of the device.

At 506, method 500 comprises forming a film comprising residual halogenatoms on the metal oxide protective layer by exposing the metal oxideprotective layer to a halogen-including compound. In some embodiments, ametal-including film may be formed on the metal oxide protective layerby exposing the metal oxide protective layer to a halogen-includingmetal compound. Non-limiting halogen-including metal compounds includeTiCl₄ and HfCl₄. In some embodiments, the film comprising residualhalogen atoms may be formed in the semiconductor processing tool orreactor used to form the gate dielectric layer and/or the metal oxideprotective layer so that a vacuum and/or air break during film stackformation may be avoided.

Residual halogen atoms included in the film formed on top of the metaloxide protective layer are measurably present in the formed film. Forexample, in some embodiments, an HfO₂ film formed from HfCl₄ may haveless than 0.5 at % Cl atoms as measured by Rutherford backscatteringspectrometry (RBS). The residual halogen atoms may originate fromreaction of the halogen-including compound during formation of the filmon top of the metal oxide protective layer. For example, halogen ligandsincluded in the halogen-including compound may remain in the film afterthe film formation process.

It will be appreciated that embodiments of method 500 may be used tobuild film stacks used in any suitable semiconductor device. FIGS. 6-7schematically depict embodiments of film stacks that may be used in theformation of a gate assembly structure for a semiconductor device.

FIG. 6 schematically shows an embodiment of a film stack 600 thatincludes a metal oxide protective layer formed according to the presentdisclosure. As shown in FIG. 6, film stack 600 includes a substrate 602,a halogen-sensitive high-K dielectric layer 604, a metal oxideprotective layer 606, and a film 608 formed on top of the metal oxideprotective layer. Substrate 602 may include any suitable substrate. Onenon-limiting example substrate includes a silicon (Si) substrate.Regardless of the type of substrate, it will be appreciated that thesubstrate may include various films and/or structures resulting fromprior processing of the substrate. In some embodiments, substrate 602may include a native surface layer of a different composition (notshown). For example, a silicon substrate may include a native SiO₂surface layer formed by exposure to ambient air.

In the embodiments shown in FIGS. 6-7, the surface of substrate 602 isplanar. However, it will be appreciated that, in some other embodiments,the substrate surface may be non-planar. For example, in someembodiments, the substrate surface may include a non-planar surfacetopography that may comprise one or more fins, troughs, vias, mesas, orother structures in any suitable density.

Halogen-sensitive high-K dielectric layer 604 is formed on top substrate602. Any suitable high-K dielectric material may be employed withoutdeparting from the scope of the present disclosure. Non-limiting examplegate dielectric materials include high-K gate dielectric materials,including transition metal oxides such as HfO₂ and alkaline earthmetal-including metal oxides such as SrTi_(x)O_(y), BaTi_(x)O_(y), SrO,and Sr_(x)Ba_((1-x)) Ti_(y)O_(z). In some embodiments, a thickness ofhalogen-sensitive high-K dielectric layer 604 may be included to adjustone or more device parameters such as EOT, drive current, thresholdvoltage, or device leakage. For example, halogen-sensitive high-Kdielectric layer 604 may include a layer of SrTi_(x)O_(y) having athickness ranging from 1 Å to 50 Å, within an acceptable tolerance.

Metal oxide protective layer 606 is formed on a top surface ofhalogen-sensitive high-K dielectric layer 604 in a suitable thickness toprevent interaction of halogen-sensitive high-K dielectric layer 604with a halogen-including compound used to form film 608. For example,thickness values may be selected based upon device performanceconsiderations, manufacturing process parameters, and/or devicearchitectural parameters, as described in some non-limiting examplesprovided below. It will be appreciated that the thickness of metal oxideprotective layer 606 may also vary according to the material included inmetal oxide protective layer 606.

Film 608 comprises a film including residual halogen atoms formed onmetal oxide protective layer 606. In some embodiments, film 608 maycomprise a metal-including dielectric material. For example, film 608may include a high-K dielectric material at a thickness selected toadjust one or more device parameters such as EOT, drive current,threshold voltage, or device leakage. In some embodiments, film 608 mayrepresent a layer of HfO₂ having a thickness 5 Å or less, within anacceptable tolerance.

In some of such embodiments, metal oxide protective layer 606 may have athickness selected based upon physical film characteristics and/ordevice electrical characteristics as well as surface sensitiveconsiderations. For example, metal oxide protective layer 606 may have athickness ranging from 1.5 Å to 5 Å, within an acceptable tolerance.Further, depending on the thickness of film selected, thewithin-substrate non-uniformity of metal oxide protective layer 606 maybe less than or equal to 13% (e.g., for a 1.5 Å film), less than orequal to 3% (e.g., for a 2.5 Å film), or less than or equal to 2% (e.g.,for a 5 Å film). Providing highly uniform films at a very thin filmthickness may provide a suitable base for deposition of film 608 whilemaintaining film stack thickness within a preselected range. This may bedesirable in some embodiments where film stack 600 represents a gateassembly.

In some other embodiments, film 608 may comprise a metal-includingbarrier material. For example, a metal-including barrier material formedbetween underlying dielectric materials in the gate assembly andconductive materials formed on top of the barrier material may preventdiffusion of the conductive material into the gate dielectric.Non-limiting examples of metal-including barrier materials include metalnitrides, such as TiN. For example, in some embodiments, film 608 maycomprise a layer of TiN having a thickness ranging from 20 Å to 500 Å,within an acceptable tolerance.

In some of such embodiments, metal oxide protective layer 606 may have athickness selected based upon surface sensitivity considerations as wellas device performance characteristics. For example, metal oxideprotective layer 606 may be selected and/or adjusted to alter or selectvarious device characteristics. In some of such embodiments, thethickness of metal oxide protective layer 606 may be selected in view ofthreshold voltage and/or EOT considerations. In such embodiments, metaloxide protective layer 606 may have a thickness ranging from 0.5 Å to 20Å, within an acceptable tolerance. It will be appreciated that suchfilms may exhibit within-substrate non-uniformity consistent with theexample metal oxide protective layers described herein.

It will be appreciated that other gate assemblies may be formedaccording to embodiments of the methods described herein. For example,FIG. 7 schematically shows an embodiment of a film stack 700 thatincludes another high-K dielectric layer 702 formed between substrate602 and halogen-sensitive high-K dielectric layer 604. In someembodiments, high-K dielectric layer 702 may be included in the gateassembly to adjust one or more device parameters such as EOT, drivecurrent, threshold voltage, or device leakage, alone or in concert withhalogen-sensitive high-K dielectric layer 604. In some embodiments,high-K gate dielectric layer 702 may include a layer of HfO₂ having athickness ranging from 10 Å to 30 Å, within an acceptable tolerance.

In some embodiments, the metal oxide protective layers and other filmsincluded in the film stacks and structures described herein may beformed using a suitable semiconductor processing tool. FIG. 8schematically shows a top view of an embodiment of a semiconductorprocessing tool 800 including a plurality of semiconductor processingmodules 802. While the depicted embodiment includes two modules, it willbe appreciated that any suitable number of semiconductor processingmodules may be provided. For example, some processing tools may includejust one module while other processing tools may include more than twomodules.

FIG. 8 also shows load locks 804 for moving substrates between portionsof semiconductor processing tool 800 that exhibit ambient atmosphericpressure conditions and portions of the tool that are at pressures lowerthan atmospheric conditions. An atmospheric transfer module 808,including an atmospheric substrate handling robot 810, moves substratesbetween load ports 806 and load locks 804, where a portion of theambient pressure is removed by a vacuum source (not shown) or isrestored by backfilling with a suitable gas, depending on whethersubstrates are being transferred into or out of the tool. Low-pressuresubstrate handling robot 812 moves substrates between load locks 804 andsemiconductor processing modules 802 within low-pressure transfer module814. Substrates may also be moved among the semiconductor processingmodules 802 within low-pressure transfer module 814 using low-pressuresubstrate handling robot 812, so that sequential and/or parallelprocessing of substrates may be performed without exposure to air and/orwithout a vacuum break.

FIG. 8 also shows a user interface 820 connected to a system processcontroller 822. User interface 820 is adapted to receive user input tosystem process controller 822. User interface 820 may optionally includea display subsystem, and suitable user input devices such as keyboards,mice, control pads, and/or touch screens, for example, that are notshown in FIG. 8.

FIG. 8 shows an embodiment of a system process controller 822 providedfor controlling semiconductor processing tool 800. System processcontroller 822 may operate process module control subsystems, such asgas control subsystems, pressure control subsystems, temperature controlsubsystems, electrical control subsystems, and mechanical controlsubsystems. Such control subsystems may receive various signals providedby sensors, relays, and controllers and make suitable adjustments inresponse.

System process controller 822 comprises a computing system that includesa data-holding subsystem 824 and a logic subsystem 826. Data-holdingsubsystem 824 may include one or more physical, non-transitory devicesconfigured to hold data and/or instructions executable by logicsubsystem 826 to implement the methods and processes described herein.Logic subsystem 826 may include one or more physical devices configuredto execute one or more instructions stored in data-holding subsystem824. Logic subsystem 826 may include one or more processors that areconfigured to execute software instructions.

In some embodiments, such instructions may control the execution ofprocess recipes. Generally, a process recipe includes a sequentialdescription of process parameters used to process a substrate, suchparameters including, but not limited to, time, temperature, pressure,and concentration, as well as various parameters describing electrical,mechanical, and environmental aspects of the tool during substrateprocessing. The instructions may also control the execution of variousmaintenance recipes used during maintenance procedures.

In some embodiments, such instructions may be stored on removablecomputer-readable storage media 828, which may be used to store and/ortransfer data and/or instructions executable to implement the methodsand processes described herein, excluding a signal per se. It will beappreciated that any suitable removable computer-readable storage media828 may be employed without departing from the scope of the presentdisclosure. Non-limiting examples include DVDs, CD-ROMs, floppy discs,and flash drives.

It is to be understood that the configurations and/or approachesdescribed herein are exemplary in nature, and that these specificembodiments or examples are not to be considered in a limiting sense,because numerous variations are possible. The specific routines ormethods described herein may represent one or more of any number ofprocessing strategies. Thus, the various acts illustrated may beperformed in the sequence illustrated, in other sequences, or omitted insome cases.

The subject matter of the present disclosure includes all novel andnonobvious combinations and subcombinations of the various processes,systems and configurations, and other features, functions, acts, and/orproperties disclosed herein, as well as any and all equivalents thereof.

1. (canceled)
 2. A method of forming a metal oxide protective layer on asurface of a halogen-sensitive metal-including layer present on asubstrate processed in a semiconductor processing reactor, the methodcomprising the steps of: providing a halogen-sensitive metal-includinglayer present on a substrate forming a metal oxide protective layeroverlying the halogen-sensitive metal-including layer, the metal oxideprotective layer derived from a non-halogenated metal oxide precursor;and forming a metal-including film overlaying the metal oxide protectivelayer by exposing the metal oxide protective layer to ahalogen-including metal compound.
 3. The method of claim 2, wherein thestep of forming a metal oxide protective layer comprises using at leasta portion of a surface of the halogen-sensitive metal-including layer.4. The method of claim 2, wherein the step of forming a metal oxideprotective layer comprises reacting an oxygen-containing reactant withan active species of the metal-including layer.
 5. The method of claim2, wherein the metal oxide protective layer is a barrier layer.
 6. Themethod of claim 2, wherein the metal oxide protective layer is a bufferlayer.
 7. The method of claim 2, where the halogen-sensitivemetal-including layer is sensitive to chlorine and where thenon-halogenated metal oxide precursor comprises a non-chlorinated metaloxide precursor.
 8. The method of claim 2, wherein the halogen-sensitivemetal-including layer comprises an alkaline earth metal-including oxide.9. The method of claim 2, wherein the halogen-sensitive metal-includinglayer comprise one or more of SrTi_(x)O_(y), BaTi_(x)O_(y), SrO, andSr_(x)Ba_((1-x)).
 10. The method of claim 2, wherein the metal oxideprotective layer excludes alkaline earth metals.
 11. The method of claim2, wherein the metal oxide protective layer comprises titanium oxide.12. The method of claim 2, wherein the metal oxide protective layercomprises aluminum oxide.
 13. A method of fabricating a semiconductordevice, the method comprising the steps of: forming a halogen-sensitivehigh-K dielectric material on a substrate; forming a metal oxideprotective layer on the halogen-sensitive high-K dielectric material;and forming a metal-including overlying the metal oxide protective layerby exposing the metal oxide protective layer to a halogen-includingmetal compound.
 14. The method of claim 13, wherein a pressure duringthe step of forming a metal oxide protective layer is ranges from 0.1Torr to 10 Torr.
 15. The method of claim 13, wherein a temperatureduring the step of forming a metal oxide protective layer is ranges from100° C. to 400° C.
 16. The method of claim 13, wherein the step offorming a metal oxide protective layer comprises using a precursorselected from the group consisting of: titanium tetraethoxide(Ti(OC₂H₅)₄), titanium tetramethoxide (Ti(OCH₃)₄), titaniumtetraisopropoxide (Ti(i-OC₃H₇)₄, and titanium tetra-n-butoxide(Ti(n-OC₄H₉)₄)); transition metal amino complexes (e.g.,tetrakis(dimethylamido)titanium (Ti(N(CH₃)₂)₄) andtetrakis(diethylamido)titanium (Ti(N(C₂H₅)₂)₄)); transition metalsilanes (e.g., tetrakis(trimethylsilylmethyl)titanium(Ti((CH₃)SiCH₂)₄)); and transition metal cyclopentadiene complexes(e.g., η8-cyclooctatetraene)(η5-cyclopentadienyetitanium (C₁₃H₁₃Ti),di-1,3-cyclopentadien-1-yl[bis(N-methylmethanaminato)]titanium(C₁₄H₂₂N₂Ti), and dicyclopentadienyl titanium diazide (C₁₀H₁₀N₆Ti). 17.The method of claim 13, wherein the step of forming a metal oxideprotective layer comprises using a precursor selected from the groupconsisting of: aluminum alkyl complexes, aluminum alkoxides, aluminumsilanes, aluminum amino complexes, and aluminum cyclopentadienecomplexes.
 18. A method of forming a metal oxide protective layer on asurface of a halogen-sensitive metal-including layer present on asubstrate processed in a semiconductor processing reactor, the methodcomprising the steps of: providing a halogen-sensitive metal-includinglayer present on a substrate using atomic layer deposition, forming ametal oxide protective layer overlying the halogen-sensitivemetal-including layer, the metal oxide protective layer derived from anon-halogenated metal oxide precursor and forming a metal-including filmcomprising residual halogen atoms overlying the metal oxide protectivelayer.
 19. The method of claim 18, wherein the film comprising residualhalogen atoms comprises a transition metal compound.
 20. The method ofclaim 18, wherein the halogen-sensitive high-K dielectric materialcomprises an alkaline earth metal-including metal.
 21. The method ofclaim 18, wherein the metal oxide protective layer has a thickness of 20Å or less.